Abstract Tobacco Center of Regulatory Science recognizes 7 categories of research priorities, of which 2 important domains are toxicity and health consequences, with emphasis on cardiopulmonary impacts of new and emerging tobacco products and ENDS. The proposed study informs the FDA in regulations regarding the comparative toxicity of e-cigarette (e-cig) flavorings using cardiovascular health, particularly pulmonary hypertension (PH) in mice as an outcome. The over-arching hypothesis is that long-term inhalation exposure (3-mo) of adolescent A/J mice to e-cig aerosols induce changes in pulmonary vasculature predisposing adult male and female mice to pulmonary hypertension, and these changes arise and/or exacerbated by flavoring-induced inflammation. Moreover, that e-cig-induced cardiovascular toxicity can be compared and the toxicity of individual flavorings graded based on the extent of adverse change. Mice (3.5-wk-of-age) will be exposed by inhalation into adulthood (4-mo-of-age) to e-cig aerosols from a self-made tank system containing propylene glycol, glycerin, nicotine and with and without flavoring; selection of flavors (vanilla, cinnamon, menthol, double apple hookah and peach schnapps) are based on human usage and published diacetyl levels. A single aim (with multiple sub-aims) is proposed: 1A) to determine whether long-term (3-mo.) inhalation exposure of adolescent mice of both sexes to e-cig aerosols (with or without flavorings) produces structural, morphological and/or molecular remodeling of the pulmonary vasculature. The toxicity of e-cig flavorings will be classified based on extent of cardiopulmonary alterations using a paradigm previously developed in this laboratory for ordering smokeless tobacco products; 1B) using the same mice exposed in SA1A to investigate the time course of effects by examining non-terminal systemic changes associated with the development of pulmonary hypertension and/or emphysema, e.g., serum markers of vascular injury and pro-inflammatory cytokines on days -30, -60, -90 during e-cig exposure; 1C) to determine persistent effects of e-cig aerosols 90 days after cessation of the 3-mo exposure on the same pulmonary hypertension and cardiopulmonary/inflammatory outcomes measured in aims 1A and 1B. Results of these studies will empower the FDA to promulgate more explicit warning labels on e-cig packaging that could, in turn, educate the public on health risks associated with use of flavored e-cigs. Moreover, unequivocal demonstration of how flavored e-cig use could lead to life-threatening health issues could result in banning the sale of specific flavorings/types of e-cigarettes. These innovative studies introduce a new and understudied public health query: e-cig use, like long-term cigarette smoking, can induce cardiopulmonary/inflammatory effects, including vascular changes in the lungs that can lead to PH, an understudied area of cardiovascular research. Identifying a relationship between vaping and PH has critical implications for setting policies/imposing regulations. These studies that assess cardiopulmonary implications of ?vaping? can begin to fill knowledge gaps on toxicity and health that to date impede the launch of new regulations.